Smoking, which is bad for you, causes premature senescence in lung fibroblasts. Since senescent cells secrete factors that encourage nearby cancers to grow, this induction of senescence could represent a major contribution to carcinogenesis by tobacco.
One open question in the field is whether tobacco (or, by extension, other toxins) have a more systemic effect on senescence throughout the body — especially because of the broad-spectrum secretory phenotype of senescent cells, some have speculated that the senescent cells formed initially at the site of carcinogen exposure could “act at a distance” and drive senescence elsewhere in the body.
Good news (against an otherwise bleak background) is provided by Müller et al., who find that skin fibroblasts from smokers show no signs of premature senescence — hence the tobacco toxins are not inducing senescence throughout the body. The authors used skin from the upper torso, which is usually protected from smoke by clothing — facial skin is exposed to sunlight, potentially confounding the results, and more to the point is directly exposed to smoke; an observation (one should say “confirmation of the obvious”) that smoking contributed to skin wrinkling via premature senescence would merely underscore what is already known.